Rosario v. Rockefeller

The deadline in question was New York's deadline for voting in party primaries. Only enrolled members of a particular political party were allowed to vote in New York's party primaries, a system known as a "closed" system of primary elections. The law stated that voters must enroll in a party by a deadline 30 days in advance of the previous year's general election. The voter could then vote in the party primary taking place after the following year's general election. The reason for the law was to prevent party "raiding," in which voters from one party enroll in the opposite party in order to have an influence on their opposing party's primary. The New York State deadline was justified on the grounds that it prevented such raiding, because the voter who wanted to join the opposing party would be put in the absurd position of enrolling in an opponent's party before voting for her own party's candidate in the general election. The Court declared that "it would be the rare politician who could successfully urge his constituents to vote for him or his party in the upcoming general election, while at the same time urging a cross-over enrollment for the purpose of upsetting the opposite party's primary."

Such raiding, the Supreme Court declared, was a negative enough result to justify the state's passing of a deadline to prevent it. Furthermore, the deadline seemed to the court to be effective. However, the petitioners argued that the deadline violated their rights under the Constitution's Equal Protection Clause, since they were effectively disenfranchised by the deadline. In their arguments, counsel for the respondents referred to several Supreme Court cases in which the Court had struck down statutes that disenfranchised particular groups of people, including Carrington v. Rash and Dunn v. Blumstein.